Catamarans



Jan. 16, 1962 Filed Sept. 4, 1959 Jan. 16, 1962 w. P. BROWN 3,016,861

CATAMARANS Filed Sept. 4, 1959 '7 Sheets-Sheet 2 Waaar/dg E .Era 14//1W. P. BROWN CATAMARANS Jan. 16, 1.962

7 Sheets-Sheet 3 Filed Sept. 4, 1959 W. P. BROWN Jan. 16, 1962CATAMARANS '7 Sheets-Sheet 4 Filed Sept. 4, 1959 Wand/H496 f? irak/f? W.P. BROWN Jan. 16, 1962 CATAMARANS '7 Sheets-Sheet 5 Filed Sept. 4, 1959W. P. BROWN CATAMARANS Jan. 16, 1962 7 Sheets-Sheet 6 Filed Sept. 4,1959 llte rates Patent iice 3,016,861 Patented Jan. 16, 1962 3,016,861CATAMARANS Woodbridge P. Brown, 3716 Campbell Ave., Honolulu, HawaiiFiled Sent. 4, 1959, Ser. No. 838,175 Claims. (Cl. 114-61) My inventionrelates to sailing craft having spaced hulls tied together by a deckthere-between and known to the public as a catamaran.

These two-hull craft are very speedy, -muh speedier than ordinarysingle-hull craft, but are at the same time readily capsized.

The principal objective of my invention is to provide a speedier craftand one which is not readily capsized.

This dual objective of my invention is had in the way the hulls areformed and joined together.

In order to more clearly bring out the present improvement a brief rsumof a catamaran structure is believed to be in order.

Catamaran hulls are usually huilt symmetrical about their ver-ticalcenter line. These symmetrical hulls require the use of deep keels,center-boards, or lee boards in order to minimize the tendency of thehull to move sidewise in the direction of the wind acting on the sail.

Another objective is to dispense with deep keels, centerboards, orlee-boards, and still prevent much of this tendency to drift leeward.This movement to leeward when the boat is moving forward sets up a dragon the hull and reduces speed.

One of the disadvantages of the catamaran is its tendency to capsizewhen the wind pressure against its sail overcomes its stability. This isdue to the relatively low center of buoyancy `of the hulls.

Therefore, it is a further objective of my invention to raise thiscenter of buoyancy as the hull tends to capsize.

When the hull keels over at an angle of 90 degrees or thereabout thecenter of buoyancy remains higher than the center of gravity thuscreating a continuing righting movement.

A still fur-ther objective of my invention is to provide a hull in whichthe tendency to heel over is continuously resisted by an inherenttendency to right itself.

How these objectives are accomplished will now be minutely described andillustrated in the accompanying drawings of which FIGS. 1, 2, and 3,thereof, are mere outline drawings of the plan, side elevation and endelevation of the catamaran with a minimum of detail. FIG. l is the planview; FIG. 2 is the side View; and FIG. 3 is the end view; FIG. 4 is anenlarged vertical section developed on the line 4 4 of FIG. 1; FIG. 5 isa diagrammatic drawing showing the relationship of the center of gravityto the center of buoyancy when the catamaran is normally upright in thewater; FIG. 6 is a similar diagrammatic drawing showing the aboverelationship when the catamaran is heeled over at 90 degrees; FIG. 7 isa diagrammatic plan showing the movement of the bow waves as they mergeand pass between the hulls when the boat is moving forward; FIG. 8 showsthe development of the hull lines looking aft; FIG. 9 shows thedevelopment of the hull lines looking forward, and FIG. 10 shows thelongitudinal lines of a hull.

Thruout the drawings and the specification similar numerals refer tosimilar parts.

Since this invention is directed to those skilled in the boat-buildingart it is assumed that these men are competent to develop the lines anddetail of a desired catamaran within the scope of the inventiondescribed and claimed. As a consequence all detail that s not absolutelynecessary to carry out the invention yhas been omitted.

The hulls 1 and 2 of the catamaran of my invention differ from theordinary catamaran hulls in that they are not symmetrical about theirvertical center line but on the contrary are asymmetrical about saidline 3 as shown in FIG. 4. FIGS. 8, 9, 'and 10 show 4the development ofthe hulls of the catamaran and each frame thereof. The verticalcurvature or contour of each rib or frame side with relation to thevertical centerline 3 is shown on FIGS. 8 and 9 while FIG. 10 shows theposition of each frame in the hull. In other words, FIGS. 8 and 9 showthat the vertical curvature or contour of one frame, as 5, diiers fromthat of an adjacent frame, as 4 or 6, and that the vertical curvature orcontour of each frame is different on each side of the verticalcenterline 3. The reason for the asymmetrical hulls will be apparent aswe proceed.

The hulls 1 and 2 include the ribs 4 covered by the skin (as plywood) 5which is stretched over the longitudinal battens `6 recessed into theribs 4 as to be flush with the exterior surface thereof. As is known tothose skilled in the boat-building art the outboard rib portion 4A andthe inboard rib portion 4B, when joined together by the deck beam 7constitute a frame, 8. Desired frames 8 may be sheathed laterally toform diaphragms 9 which serve to strengthen the hulls and formwater-tight compartments in said hulls. FIG. 4 shows how these frames 8may be braced. l t

The spaced hulls 1 and 2 of the catamaran are tied together at theframes by the botto-m tie members 10 positioned along a line as 11,shown in FIG. 4, to form the iloor 19A of the intermediate or tieportion 12. See FIGS. 3 and 4 too. The upper members 13 of theintermediate tie portion 12 may be sheathed over as a continuance of thedeck portion 7A of the hulls 1 and 2.

Desired portions of this intermediate tie portion 12 may be formed andcovered to provide a cabin 14 as suggested by the dotted outline in FIG.4. This intermediate -tie portion 12 also provides support for thecatamaran mast 15. It is to be noted in FIG. 4 that this intermediatetie portion 12 bridges the two hulls 1 and 2 at a point considerablyabove the water line indicated at 16 in said figure. This FIG. 4 clearlyshows the relation of the hulls 1 and 2 to each other and to ltheirrespective vertical centerlines 3 which are on 1l 6" centers in a 34catamaran.

The inboard rib portion 4B of each hull, as shown in FIG. 4, is smoothlycurved up to the junction with the bottom tie member 10 of theintermediate tie portion 12, with the curvature of each inboard ribportion 4B being oppositely curved with respect to the other. Since thetwo spaced hulls 1 and 2 are similarly but oppositely curvedlongitudinally too it is apparent from a perusal of FIG. 7 that a planebetween the hulls at the waterline would have the general configurationof a Venturi throat. As a consequence the how wave from one hull isdeected toward the bow wave from the other hull. When the catamaran ismoving slowly the bow waves converge at approximately the mostconstricted portion of the throat 17, and as the catamaran speeds up theconvergence takes place further aft of said most constricted portion.The inboard side of my catamaran hulls have a greater longitudinalcurvature than -the outboard side thereof hence a low pressure area isbuilt up adjacent the inboard sides and the water fills in the suctionor vacuum area created to the rear of the throat 17. The result is thatthe speed of the catamaran forward is increased. FIG. 7 has indicatedthereon the longitudinal lines of the hull at the water line and theirrelation to the centerlines of the hulls.

The formation of the outboard rib portion 4A, and inproximately thewater'line '16 lin a substantially straight line deected from thevertical hull center line 3. At approximately the water line 16 theVoutboard rib portion 4A starts to curve outwardly and upwardly and thenback approximately parallel to the center line 3 before it reaches thedeck line 7A.

VThis straight face portion 19 below the water line 16 serves tominimize the drift to leeward against the action of the wind against thesail as the catamaran moves forward. As a consequence the means nowemployed -to minimize this drift, such as deep keels, center-boards, andlee-boards may be dispensed with. When the above mentioned means aredispensed with the drag on the hull they create is also dispensed with'.As a result 'the speed ofthe catamaran is increased.

The bulging curvature of the outboard rib portion 4A, described above,permits the center of buoyancy to be positioned outboard from thever-tical center line 3 and above the center of gravity. These centersare designated by'the numerals B and G, respectively, in FIGS. 5 and 6.Just what takes place when the catamaran starts to heel over is clearlyillustrated inthe above iigures without further description.

v-lin addition to the safety feature the bulging structure shown anddescribed permits another advantage to be had, namely, additional cubichull content without adding -to the beam of vthe hull at the water line.

It is believed that one skilled in the boat-building art may adapt myinvention, set forth in the appended claims, to catamarans of greater orless length and beam, therefore,

I claim all that cornes fairly within the scope of said appended claims.

' I claim:

1. A'catamaran hull having both sides thereof vertically curved with thesides asymmetrical -to the vertical center line of said hull and bothsides horizontally curved withv the sides asymmetrical 4to .thelongitudinal center line ofthe hull said horizontal curvature beingcontinuous from stem -to stern and said longitudinal center line beingstraight from stem to stern.

2'. A catamaran having a pair of hulls spaced apart laterally one fromthe other and having their adjacent inboard sides similar inconfiguration and their outboard sides of similar configuration but of aconfiguration different from the configuration of the inboard sides bothi sides of each hull being vertically curved and asymmetrical to thever-tical center line of said `hull and horizontally curved with thesides asymmetrical to the longitudinal centerline of the hull saidhorizontal curvature being continuous fro-m stern to stern and saidlongitudinal center line being straight from stem to stern.

3. A catamaran having a pair of hulls spaced apart laterally and meansto tie said hulls together, including a deck portion positioned abovethe water line when the hulls are afloat, said hulls having similaroppositely disposed inboard sides convexly curved vertically from keelto bottom of the deck portion and convexly curved longitudinally fromstem to stern and having similar oppositely disposed outboard sidesconvexly curved longitudinally from stem to stern said outboard sideshaving a straight flare from'keel to water line and a reverse curve fromthe water line to the deck portion the convex portion of said reversecurveybeing adjacent the deck portion.

4. A catamaran having a pair of hulls spaced apart laterally andconnected above the normal water line by a deck portion, the center ofgravity of the hulls and deck portion being above said water line whenthe hulls are aoat in an upright position with the center of buoy- .ancybelow said water line, said hulls having similar `oppositely disposedinboard sides convexly curved vertically from keel to deck portion andconvexly curved longitudinally from stem to stern and having similaroppositely disposed outboard sides convexly curved longi -tudinally fromstem to stern, said outboard sides having a straight are from keel tothe Water line and a reverse curve from the water line -to the deckportion the convex portion of said reverse curve being adjacent the deckporltion said last named convex curvature encompassing a hull portionwhich when submerged brings the center of .buoyancy below and ahead ofthe center of gravity whereby the center of gravity acts to provide apositive righting rnornent to return the catamaran -to its formerposition.

5. A catamaran having a pair of spaced asymmetrical hulls oppositelydisposed, each hull having a plurality of pairs of ribs each pair ofsaid ribs being joined top and bottom to form a frame each outer face ofwhich has a vertically curved contour, the contour of one side of saidframe differing from the contour of the opposite side of Vsaid frameboth contours being equally spaced from the hull'centerline at .the topof the frame only, the frame contour on the'inboard side of the hullbeing substantially convex throughout and the frame contour on theoutboard side of the hull having an outwardly ared bottom portion and aconvex top portion said portions being joined by an interveningoutwardly ared concave portion.

References Cited in the le of this patientA UNITED STATES PATENTS295,153 David Mar. 18, 1884 1,093,475 Rosing Apr. 14, 1914 1,712,281Royer May 7, 1929 1,712,758 Durand May 14, 1929 1,941,586 Snadeck Jan.2, 1934 2,464,957 Wood Mar. 22, 1949

